FN is present in many body fluids and on the surface of numerous cells. It is implicated in a variety of important biological processes including cell adhesion, connective tissue formation, organogenesis, reticuloendothelial system function, malignancy and metastasis, hemostasis and wound healing. Interaction of FN with collagenous tissue is likely to be crucial to its function in these processes. The aim of this project is to study and characterize the interaction between defined fragments of the ligand-binding high molecular weight glycoprotein fibronectin (FN) and fragments of denatured collagen (gelatin). Of particular interest are the effects of heparin on the FN fragment-gelatin fragment interactions. Our specific objectives are to:A. Study the binding of four well-characterized fragments of human plasma fibronectin (FN) derived from the N-terminal region, each containing the G/C domain, with a FN-binding cyanogen bromide fragment prepared from commercial porcine skin gelatin. We will compare the strength of binding of the FN fragments to gelatin fragments in the presence of heparin and other potential modulators by measurement of association constants between FN fragments and fluorphore-labeled gelatin fragment using fluorescence polarization in the fluid phase. These methods were chosen to study interactions which may occur within the FN molecule upon binding of ligands to adjacent domains. The fluid phase fluorescence polarization system will be extended to study binding of FN fragments with native soluble collagen through competition experiments using the fluorophore- labeled gelatin fragment as a primary probe. B. Expolore by chemical modification procedures the specific structural features of the isolated FN 40 kDa G/C domain which may be critical to its binding with collagen by modifying 1) cationic lysine and arginine residues, 2) aromatic tyrosine and tryptophan residues, and 3) N- glycosyl carbohydrate chains. Modifications will emphasize differential labeling of residues "protected'' in the presence of bound collagen derivatives to identify the "active site" for the collagen-FN interaction. Quantitative studies of the molecular details of these interactions of FN and its domains should yield data which is of both physiological and pharmacological significance.